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llmrao TATES PATENT OFFICE.

MILTON H. CAMPBELL, OF NEW YORK, N. Y., ASSIGNOR TO HIMSELF AND NORVIN GREENE, OF SAME PLACE.

PROCESS OF ELECTROPLATING WITH AN ALLOY F PLATINUM AND-SILVER.

SPECIFICATION forming part of Letters Patent No. 248,554, dated October 18, 1881.

Application filed August 1,1881. (No specimens.)

To all whom it may concern:

1 Be it known that I, MILTON H. CAMPBELL, of the city, county, and State of New York, have made a new and useful Improvement in 5 theArtofElectroplatingSilverorSilver-Plated Articles or Goods for the Purpose ofProtecting their Surfaces from Corrosion and Tarnishing, which consists in coating such articles with a homogeneous alloy consisting of platinum and silver; and to this end I employ an anode for the electroplating-bath, which is a homogeneous alloy of platinum and silver. In making a plating-solution to be used with this anode for the bath a portion of the homogeneous alloy is converted into a compound chloride of platinum and silver, which is washed and dissolved in a solution of cyanide of potash.

To obtain the best results, about thirty-six parts of platinum should be alloyed with sixtyfour parts of silver, though I have found that there may be a wide departure from these proportions. Twenty-five parts of platinum and seventytive of silver may be advantageously employed. However, it" less than ten parts of platinum be alloyed with itslarge supplement of silver, the alloy will not be capable of resisting the action of the stronger corrosive agents, such as nitric acid and the sulphides. In the preparation ot'the compound chloride of platinumandsilversomeofthehomogeneousalloy ofplatin um and silver isdissolved in nitric or nitro muriatic acid, whichis heated to the boiling-point, and isdilutcd with about four times its volume of water, though this proportion of 3 5 water may be greatly varied. To this solution is added a saturated solution ofchloride of ammonia in hot water, whence a compound chloride of platinum and silver is precipitated.

The manner in which I treat the compound 40 chloride of platinum and silver preparatory to its use in the bath is analogous to the wellknown method employed for dissolving chlo: ride of silver for a silver solution for electroplating, which is, the compound-chloride precipitate is washed and dissolved in a solution of cyanide of potash. About an ounce of the compound chloride is dissolved in one gallon of water, more or less, with a sufficient quantity of cyanide of potassium added thereto to afford a clear solution.

In carrying out my invention it is necessary to employ an anode for the electroplating-bath, consisting of a homogeneous alloy of platinum and silver, also a solution for the electroplating-bath, having therein the compound chloride of platinum and silver, as specified. These features, however, I desire to specifically disclain from this application and to make them-1 the subject-matter of another application for a patent.

What I claim, and desire to secure by Letters Patent, is-' 1. The method of protecting silver or silverplated surfaces from corrosion or tarnishing, which consists in electroplating said surfaces with an alloy of platinum and silver.

2. A metallic article whose surface is coated with an electro-deposited alloyof platinum and silver.

3. The method, as specified, of obtaining the compound chloride of platinum and silver, which consists in dissolving the alloy of platinum and silver in nitric acid or its equivalent, and in'addiug thereto chloride of ammonia to ett'ect aprecipitation ofsaid compound chloride.

MILTON H. CAMPBELL.

Witnesses:

S. It. GRAMMER, WM. ARNOUX. 

